Effect of microbubbles on membrane fouling due to protein in water treatment processes

In water treatment processes, an ultrafiltration (UF) membrane is usually used for drinking water production from surface water and for reclaimed water production from wastewater. Membrane fouling due to the deposition of various foulants on the UF membrane surface and pore blocking is a major problem. It has already reported that application of microbubbles (MBs) reduces the fouling. However, the mechanism is not clear yet. Thus, in this study, the mechanism of reducing fouling, especially the fouling due to proteins, by MBs was investigated using bovine serum albumin (BSA) as a model foulant. The filtration was done with a cross flow filtration unit. MBs were applied into the feed solution just before the inlet of UF module. A retentate and an overflow were returned into the feed tank. It was found that BSA were denatured and coagulated by the application of MBs. The coagulated BSA floated in the feed tank and then, the BSA concentration at the bottom of feed tank decreased. Thus, when the feed was suctioned from the bottom of feed tank, the fouling was reduced as well as a decrease in BSA concentration.